Conventionally, among the image forming apparatus forming an image by the electrophotography method, there have been ones in which a photoreceptor is charged by an electrostatic charger with a non-contact type discharge electrode fixed in a shielding case having an opening. The electrostatic charger performs corona discharge (hereinafter, simply referred to as a discharge) to the photoreceptor from a tip portion of the discharge electrode to which a high voltage is applied, thereby causing the photoreceptor to be charged with electricity.
In the electrostatic charger, the ion wind occurring at the time of the discharge causes the air to flow in from the opening of the shielding case, and this in turn causes a circulation of air to occur inside the shielding case. At that time, if dust flows in from the outside of the shielding case, then the dust sticks to the discharge electrode. The dust sticking to any place other than the tip portion of the discharge electrode may not cause any problem; however, when the dust sticks to the tip portion of the discharge electrode, a discharge irregularity occurs due to the hindrance to a uniform discharge, thereby making it difficult for the photoreceptor surface to be charged uniformly.
For this reason, among the conventional electrostatic chargers each comprising a discharge electrode are ones in which the dust is prevented from sticking to the discharge electrode by diverting the ion wind to the opening of the shielding case by means of taking the air into the shielding case from a slit formed at the bottom of the shielding case (e.g., refer to Patent Literature 1).